Several studies clearly support the notion that a lower resting heart rate is linked to improved survival. In the general population, several studies have shown a strong positive correlation between higher resting heart rate and increased mortality. A two- to three-fold increase in mortality is observed for males with a resting heart rate higher than 88 beats pr. minutes (bpm) compared to a group of males with less than 65 bpm. The heart rate is not only related to cardiovascular mortality but seem also to relate to death from other causes such as cancer. It has even been hypothesized that there is a relation between low heart rate and life expectancy in general (Zaza et al., 2001).
The most common form of cardiovascular disease in the industrialized countries today is coronary artery disease (CAD) or coronary heart disease (CHD) which is the leading cause to heart attacks. CAD and CHD is a “hardening” of the arteries on the surface of the heart, where the term “hardening” refers to a condition that causes the arteries to become so narrowed and stiff that the free flow of blood is blocked.
Lower heart rate is related with better outcome and in particular with a reduced risk of arrhythmias. Higher heart rate may reflect a higher metabolic rate and lower vagal tone thus increasing ischemic risk. Furthermore higher heart rates may also deteriorate ventricular function (Lombardi, F in Zaza et al., 2001). Thus it is not surprising that it has been reported that an important risk factor associated with CAD or CHD is a high heart rate. CAD or CHD is frequently treated with medications. These medications fall into different categories such as:
1. Beta blockers that reduce the workload of the heart by blocking certain chemicals from binding to beta-receptors in the heart.
2. Nitrates that work directly on the blood vessels, causing them to relax and allowing more oxygen-rich blood to reach the heart.
3. Calcium channel blockers that increase blood flow through the heart and may reduce the workload of the heart by blocking calcium ions from signalling the blood vessels to constrict or tighten.
4. Anti platelets (e.g. aspirin) that inhibit the formation of blood clots by decreasing the ability of platelets (microscopic particles found in the blood) to bind together and form a blood clot.
The prevention of a high heart rate in the early stage of the development of the disease can be an alternative to treatment of high heart rate with drugs. A large number of food derived bioactive compounds are currently considered as beneficial for the general well being or as health promoting.
It is known that milk fermented by lactic acid bacteria (LAB) may produce anti-hypertensive effects due to the liberation of peptides from casein in the milk by the proteolytic activity of the lactic acid bacteria. This is for instance described in EP821968 (Calpis Food Industry), EP1016709 (Calpis Food Industry) and WO0132836 (Valio Ltd.).
The article of Yamamoto et al. (1996) discloses that milk fermented with a starter containing Lactobacillus helveticus and Saccharomyces cerevisiae reduces the systolic and diastolic blood pressure, yet no changes were observed in other indexes, including pulse rate.
WO0185984 (Davisco International Foods, Inc.) also relates to peptides having anti-hypertensive effect (blood reducing effect), where the peptides from an enzymatic digest of whey protein. Changes in heart rate and blood pressure were measured. A significant reduction in mean arterial blood pressure was observed, and except for the observation of the 75 mg/kg dose, which elicited a decrease in heart rate, no significant difference between the heart rate responses occurred at the doses of 30 and 150 mg/kg.
The article of Fuglsang, A., et al. (2002) describes, as the article of Yamamoto et al. (1996), that fermented milk peptides have anti-hypertention properties. However, on page 3569, 1. column, 2. paragraph, it is stated in relation to the tested samples that “the heart rate effect was insignificant versus that of unfermented milk” (i.e. placebo) indicating that the effect on the heart rate was considered insignificant.
The above mentioned article of Yamamoto et al. (1996) and article Fuglsang (2002) and the WO0185984 document indicates that although a lactic acid bacterium fermented product has blood pressure reducing properties there are no reason to believe that it should have heart rate reducing properties as well.